The LFT on a hockey betting line stands for Lose by Fewer Than. These types of wagers are known as puck line bets, which is hockey's version of betting against the spread.
When you are making this kind of wager, you are betting the underdog will lose by fewer goals than listed on the line.
For example, if you pick an underdog that is listed at +1.5 you will win the bet if it loses by one goal or less. The underdog will also produce a winning wager if it wins the game. For the favored team to produce a winning bet, it must win the game by two goals or more based on it being listed at -1.5.
The vast majority of puck lines for the National Hockey League list the favorite as -1.5. The reason the line is so low is because most NHL games are low-scoring, and therefore there's often not much of a difference between the two teams in the final score. Many games are decided by one goal or two and the bookmakers are splitting the difference by listing the game with a 1.5 line.
Another way to understand this is simply to deduct a 1.5 goal total from the favored team or add a 1.5 goal total to the underdog team before the game gets started. After you factor in the handicap goal total, the team with the higher score will produce the winning bet.
The reason a .5 is added to the 1 on the line is to make sure bets have winners or losers. If the line were to be listed as simply a 1 or a 2, many bets would end in ties, which is also known in betting parlance as a push. Unless you made a wager on the game to end in a draw after regulation time (60 minutes), a push would result in gamblers getting their money back because they neither won nor lost their bet.
Many people who bet the LFT in hockey tend to do so because puck lines often offer better odds than a moneyline bet. With a moneyline bet, you are just picking which team you think will win the game. If you think the game will be close or the underdog has a chance to produce an upset win, betting on the underdog gives you a one-goal cushion because it does not have to win the game for you to win the bet.
Another attraction with a puck line bet - as opposed to a moneyline bet in hockey - is the fact many games go to overtime. In overtime the first goal wins the game, meaning the final score will be no more than a one-goal differential. An overtime game will therefore always result in a winning LFT bet. This also applies to games that go to a shootout after neither team scores in overtime. The team that wins a shootout will be listed as having won the game by one goal, no matter how goals were scored during the shootout.
When making an LFT bet, important things to consider include whether the teams tend to play close scoring games and the past history of the scores between the two teams.